A short answer to a shallow question. There are two types of voice over, ones for which you are right, and those for which someone else is right. Or, you could say that there are jobs that provide steady income and those that are completed in one session.

A simple techniqe taught to me by Dr. Morton Cooper, PhD. Dr. Cooper was the head of Speech Pathology at UCLA for decades. If you are forcing your voice into your throat or chest in an effort to sound like what YOU THINK is marketable, STOP! You are damaging your voice and your reputation.Dr. Cooper's method is a healthy and responsible cure.

This answer is a means to conduct your search for training. You have to find the coach and the approach that is right for you.

A short podcast to address a common thread.

Old School means: Fundamentals, Discipline, and Respect For The Game. Training for a career means deliberate correct practice of those fundamentals over time. You practice the fundamentals until you get a 'feel' for them, until you can tell without thinking that you are working correctly. Then, you can play.